Semiconductor device and layout design method therefor

ABSTRACT

A layout design method for a semiconductor device includes a step of arranging transistors, a dummy gate forming step of forming dummy gates, which has a shape identical with a shape including gate electrodes or the gate electrodes and projected parts from active regions of the gate electrodes, in positions in parallel with and a fixed distance apart from the gate electrodes arranged at both ends in a gate length direction on active regions of the transistors and, when the transistors have plural gate electrodes with different gate widths, extending the projected parts to the outside of the active regions by a necessary length, a gate connecting step of, when gate patterns and contact regions are connected to the gate electrodes of the transistors, connecting the gate electrodes and the dummy gates according to a positional relation between the gate electrodes and the dummy gates, and a wiring step of wiring a metal layer. It is possible to design a semiconductor device having a smaller area than that in the past and with a less design man-hour.

RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.11/149,350, filed Jun. 10, 2005, claiming priority of JapaneseApplication No. 2004-174329, filed on Jun. 11, 2004, the entire contentsof each of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device and a layoutdesign method for the semiconductor device, and in particular to asemiconductor device and a layout design method for the semiconductordevice that arrange dummy gates in order to control fluctuation inshapes of gate electrodes of transistors.

2. Description of the Related Art

There is known a layout design method of arranging dummy gates inpositions a fixed distance apart from gate electrodes of transistorssuch that gate patterns are arranged at equal intervals in order tocontrol fluctuation in shapes of the gate electrodes of the transistors.JP-A-2000-200882 (FIG. 1) and JP-A-2000-223663 (FIG. 1) described belowmention that the dummy gate is formed in a process identical with thatfor a gate electrode of an adjacent transistor, has an composition and ashape identical with the gate electrode, and is floating in terms of apotential, connected to a power supply potential, or grounded.

In addition, a JP-A-2002-26125 (FIG. 1) mentions that all gate patternsare formed to match a gate electrode having a longest active region.

However, when layout design is performed to arrange a dummy gate betweentransistors such that gate patterns are arranged at equal intervals,compared with the case in which a dummy gate is not arranged, a man-hourfor arranging the dummy gate and design rules, which should beconsidered because of the arrangement of the dummy gate, increase. Thus,it is possible that a layout design man-hour and at area increase.

For example, as a layout design method, it is conceivable to adopt adesign method of arranging transistors and dummy gates in advance suchthat gate patterns are arranged at equal intervals and performing awiring step after that. However, when such layout design is performed,in particular, in a semiconductor device like a memory for which alayout has to be designed within a fixed pitch width or, for example, inorder to perform layout design taking into account a yield such as anarrangement of two contacts, it may be inevitable to increase an area ina vertical direction of a pitch width to keep gate patterns within apredetermined pitch width because of restriction of design rules amongthe gate patterns. In the worst case, it may be inevitable to rearrangethe transistors and the dummy gates to repeat the design.

Specifically, the problems will be explained with layout design for alatch circuit shown in FIG. 33 as an example. Here, in order to explainthe problems plainly, a layout structure is shown and explained only foran area 33(A) surrounded by a dotted line.

FIG. 34 is a layout in which transistors in the area of 33(A) in FIG. 33are arranged in a state in which the transistors share source/drainregions as much as possible and dummy gates are arranged to match alargest gate width of gate electrodes provided in the transistors.

Here, pt1 is set as a pitch width in an x direction in the figure thatis determined in advance because of design restriction. NW indicates anN-WELL region and other parts are assumed to be a P-WELL region. D_NWand D_PW are active regions that are arranged on N-WELL and P-WELL andused for fixing respective regions in a substrate at a power supplypotential or a ground potential. DC indicates contacts.

TR1 to 4 are transistors and GA1_1 to GA1_4, GA2_1 to GA2_2, GA3_1 toGA3_4, and GA4_1 to GA4_2 are gate electrodes on the transistors TR1 to4. EXT_GD is a length of projected parts to the outside of the activeregion of the gate electrodes.

Dummy gates DG30, 31 connect gate patterns, which are formed to bearranged in parallel with the gate electrodes on TR1 to 2, and TR 3 to 4(in a y direction in the figure) and over a region including theprojected parts in a gate width direction of all the gate electrode (inthe y direction in the figure). Here, an interval in a gate lengthdirection (an x direction in the figure) between gate patterns of thedummy gates and between the gate electrodes and the dummy gates is afixed space SP_GA_L. The interval is set to a predetermined length thatprevents fluctuation in shapes of the gate patterns. In addition, awidth in a gate length direction of the respective gate patterns of thedummy gates (the x direction in the figure) is a minimum gate lengthLG_min of the gate electrodes.

As shown in FIG. 34, when a transistor has plural gate electrodes withdifferent gate widths, a dummy gate is formed on an extended line in agate width direction of the gate electrodes. For example, the gateelectrode GA1_2 has a small gate width compared with the gate electrodeGA1_1 and it is necessary to arrange gate patterns over both ends in agate width direction of the gate electrode GA1_1. Thus, a dummy gate isformed in a position a minimum spacing SP_GA_min apart from the gateelectrode GA1_2 in the gate width direction (in the y direction in thefigure) between the gate patterns as encircled by (A1).

As opposed to FIG. 34, FIG. 35 is a diagram in which contact regions forconnecting with the gate electrodes are formed and wired using one-layermetal M1. CGMA20 to 28 are regions in which contacts for connecting agate layer and a metal layer are arranged, which are herein afterreferred to as gate contact regions. SP_M1_min is a minimum spacing ruleof the one-layer metal.

In usual layout design, in particular, layout design for a memory,wiring is made by one-layer metal as much as possible. Metal wiringlayers of a second layer and upper layers are often used for globalwiring for propagation in a long distance such as a power supply wiringand a clock. In this example, wiring by the one-layer metal is performedas much as possible. However, CGMA20 and CGMA21 as well as CGMA24 andCGMA25 cannot be connected unless two-layer metal is used because ofrestriction of wiring by the one-layer metal.

In (A2) to (A6) encircled by an alternate long and short dash line, thegate contact regions CGMA20, 23, 24, 26, and 28 and the dummy gates DG30and 31 are required to be arranged complying with the spacing ruleSP_GA_min between gate patterns. In (A7) and (A8), the gate contactregions GCMA22 and 23 as well as the gate patterns connecting CGMA27 andCGMA28 are required to be arranged complying with the spacing ruleSP_GA_min between gate patterns. In (A9) and (A10), the gate contactregion CGMA22 and D_PW as well as CGMA27 and D_NW are required to bearranged complying with a spacing rule between a gate pattern and anactive region. As a result, a layout area increases in the y directionin the figure. In addition, in order to secure a yield, it is desired toarrange two or more contacts between metal and gates as much aspossible. However, in all the gate contact regions other than GCMA20,21, and 23, it is impossible to arrange two contacts because of designrules between metals, gate patterns, and the like around the gatecontact regions and restriction in terms of an area.

As opposed to FIG. 35, FIG. 36 is a diagram in which a contact CMbetween the one-layer metal and the two-layer metal is arranged onCGMA20, 21, 24, and 25 and CGMA20 and 21 as well as CGMA24 and 25 areconnected by the two-layer metal M2. Therefore, when global wiring ismade by two layers of metal on such a layout, it is likely that an areaincreases because of these wirings.

As described above, in the conventional layout design method, dummygates having a length matching a gate electrode with a largest gatewidth are formed to be arranged over both ends in a gate width directionof gate electrodes of all transistors. Thus, positions where gatepatterns and gate contact regions connecting with the gate electrodescan be arranged are restricted by a minimum spacing rule between thegate contact regions and the dummy gates. As a result, it is inevitableto reduce the number of contacts or a layout area increases.

In addition, in the arrangement of the gate contact regions, it isnecessary to consider a design rule between the gate contact regions andthe dummy gates and a metal wiring connecting with the gate contactregions. Thus, layout design is complicated and a design man-hourincreases compared with the conventional semiconductor device withoutdummy gates. In many signal wirings, it is necessary to consider aninfluence of an area an influence among signals. When wiring correctiondue to the influences occurs, since it is necessary to consider a designrule for the dummy gates with respect to original layout design, designis complicated and a design man-hour further increases.

In order to place a layout within a predetermined pitch, if transistorsand dummy gates are arranged to be placed within the pitch in an initialstage and contact regions and metal wirings are set to match thearrangement, when a design rule cannot be met once, it is likely thatall the transistors, dummy gates, contacts, and wirings have to be movedand corrected in the worst case. In such a case, a design back trackingman-hour is large. As a method to avoid such a case, it is possible tochange the number of contacts to be arranged from two to one. It isrecommended not to take such an avoidance method if possible from theviewpoint of improving a yield.

As described above, the conventional layout design method forsemiconductor devices includes many factors causing an increase in anarea and a design man-hour or a decline in a yield in arranging dummygates.

SUMMARY OF THE INVENTION

The invention has been devised in view of the circumstances and it is anobject of the invention to provide a semiconductor device that preventsan increase in a chip area and an increase in a design man-hour and issmall, and highly reliable, and is made efficiently.

It is another object of the invention to provide a semiconductor deviceand a layout design method that reduces a layout area and a designman-hour in a semiconductor deice that arranges additional gate patternsfor controlling fluctuation in shapes of gate electrodes of transistors

In order to solve the problems, the applicant has found that it ispossible to prevent an increase in an area and a design man-hour due toa design rule between dummy gates and gate electrodes by, based onshapes of and positional relations among transistors, gate electrodes ofthe transistors, gate patterns and gate contact regions connecting withthe gate electrodes of the transistors, and dummy gates, automaticallyforming the dummy gate, connecting the dummy gate and the gateelectrodes, or changing shapes of the dummy gates. In particular, theapplicant has confirmed that, in a logic system circuit, there is noproblem in terms of circuit characteristics even if gate electrodes anddummy gates having an area substantially the same as that of the gateelectrodes are connected and there is no problem in formation of thegate electrodes either. On the basis of this knowledge, the inventionhas been devised. Note that, here, the dummy gates, which are originallyprovided to improve pattern accuracy, functions exceeding a role of theoriginal dummy gates because of electrical connection with the gateelectrodes, for example, functions as contact regions. Therefore, thedummy gates are assumed to be first to fifth additional gate patternsdescribed below.

The semiconductor device of the invention is characterized by includingfirst and second additional gate patterns that are formed in parallelwith and at a fixed distance from a gate electrode of a first transistorand in a process identical with that for the gate electrode and have acomposition identical with that of the gate electrode, and in that thefirst additional gate pattern and the second additional gate pattern arearranged to be asynchronous to the gate electrode.

With this constitution, the first and the second additional gatepatterns are always a fixed distance apart from the gate electrode, butdo not always have the same length or width as the gate electrode andcan be changed in a shape. Thus, a degree of freedom of design increasesand it is possible to prevent an increase in a design man-hour.

The semiconductor device of the invention includes a semiconductordevice in which the first additional gate pattern is electricallyconnected to the gate electrode by a third additional gate pattern.

With this constitution, since the gate electrode and the firstadditional gate pattern are connected by the third additional gatepattern, the first additional gate pattern, the gate electrode, and thethird additional gate pattern are not restricted by a design rulebetween gate patterns. Thus, an area can be reduced. In addition, it ispossible to perform layout design taking into account fluctuation inshapes of gate electrodes.

The semiconductor device of the invention is characterized in that thefirst additional gate pattern includes a position vector component thatis different from that of the gate electrode.

With this constitution, the first additional gate pattern is always afixed distance apart from the gate electrode, but does not always havethe same length and width as the gate electrode and can be changed in ashape. Thus, a degree of freedom of design increases.

In the semiconductor device of the invention, the first additional gatepattern is arranged such that a width changes in a gate length directionof the gate electrode.

With this constitution, the first additional gate pattern serving as adummy gate is controlled in a width rather than a length that affects agate pattern significantly. Thus, it is possible to change a designrelatively freely without deteriorating pattern accuracy of the gateelectrode.

In the semiconductor device of the invention, the first additional gatepattern is arranged such that a width changes stepwise in a gate lengthdirection of the gate electrode.

With this constitution, since the width changes stepwise, it is possibleto reduce an entire area of the semiconductor device by controlling anarea of the first additional gate pattern to be necessary minimum tosecure an area in which other gate patterns can be arranged. This makesit possible to change a design relatively freely without deterioratingpattern accuracy of the gate electrode while minimizing influences onthe gate electrode and the additional gate patterns connecting with thegate electrode.

In the semiconductor device of the invention, the first additional gatepattern is connected to a potential different from a power supplypotential and a ground potential.

The semiconductor device includes a gate electrode of a designedtransistor and first and second additional gate patterns that arearranged in parallel with and at a fixed distance from the gateelectrode and formed in a process identical with that for the gateelectrode and have a composition identical with that of the gateelectrode, and in that the first additional gate pattern is electricallyconnected to the gate electrode by a third additional gate pattern, isnot floating in terms of a potential, and is not connected neither apower supply potential nor a ground potential.

With this constitution, in creation of a gate pattern for connection tothe gate electrode, the pattern of the gate electrode and the firstadditional gate pattern are connected, whereby the gate electrode andthe first additional gate electrode are not restricted by a design rulebetween an additional gate pattern and a gate pattern. Thus, it ispossible to reduce an area and it is possible to perform layout designtaking into account fluctuation in shapes of gate electrodes.

The semiconductor device of the invention includes a semiconductordevice in which the second additional gate pattern is always floatingelectrically.

Consequently, there is an effect that a degree of freedom of layoutdesign increases by controlling an increase in an area for electricalconnection such as wirings and contact regions.

The semiconductor device of the invention includes a semiconductordevice in which the second additional gate pattern is connected to apower supply potential or a ground potential.

Consequently, it is also possible to use additional gate patterns notonly for controlling fluctuation in gate electrodes but also ascapacitive device for fixing a power supply potential or a groundpotential.

The semiconductor device of the invention includes a semiconductordevice in which the first additional gate pattern has a small areacompared with the second additional gate pattern.

With this constitution, even when it is necessary to connect gateelectrodes and additional gate patterns because of restriction in termsof an area, it is possible to reduce a load on the gate electrodes byconnecting the gate electrodes to additional gate patterns with asmaller area.

The semiconductor device of the invention includes a semiconductordevice in which the first additional gate pattern is formed on an activeregion.

The semiconductor device of the invention includes a semiconductordevice in which the first additional gate pattern is formed from anactive region to an inactive region.

The semiconductor device of the invention includes a semiconductordevice in which the first additional gate pattern is formed on aninactive region.

The semiconductor device of the invention includes a semiconductordevice in which a contact for connecting the first additional gatepattern to a metal wiring layer is arranged on the first additional gatepattern.

With this constitution, even when a contact region connecting gate andmetal layers cannot be arranged in a projected part of the gateelectrode because of wiring restriction of a metal wiring and isrequired to be arranged around the first additional gate pattern, it ispossible to control an increase in an area by arranging the contactregion on the first additional gate pattern and connecting the contactregion to the gate electrode.

The semiconductor device of the invention includes a semiconductordevice in which at least two or more contacts are arranged on firstadditional gate pattern in parallel with the gate electrode of the firsttransistor and at a fixed interval from the gate electrode.

With this constitution, since the two or more contacts are arranged onthe first additional gate pattern, it is possible to control a declinein a yield. In addition, the contacts are arranged in parallel with thegate electrode and layout design is performed complying with a wiringpitch with a metal wiring connecting with source and drain regions of atransistor. This makes it possible to control an increase in an area ofan entire layout due to an increase in an area of a metal layer.

The semiconductor device of the invention includes a semiconductordevice in which the first additional gate pattern has a shape identicalto a shape of the gate electrode of the first transistor or a shapeincluding the gate electrode and the projected part thereof to theactive region.

With this constitution, the first additional gate pattern includes theshape identical to the gate electrode of the transistor and theprojected part in condition with area restriction. Thus, it is possibleto further reduce fluctuation in shapes of gate electrodes.

The semiconductor device of the invention includes a semiconductordevice in which the first additional gate pattern and a fourthadditional gate pattern, which is arranged a fixed distance apart fromthe first additional gate pattern in a gate width direction of the firsttransistor, are arranged at least over both ends in the gate widthdirection on the active region of the gate electrode of the firsttransistor.

With this constitution, it is possible to reduce a load by reducing alength in a gate width direction of an additional gate patternconnecting with gate electrodes of transistors and control fluctuationin shapes of gate electrodes of transistors by arranging anotheradditional gate pattern on an extended line.

The semiconductor device of the invention includes a semiconductordevice in which the first additional gate pattern and the fourthadditional gate pattern are arranged over the both ends in the gatewidth direction on the active region of the gate electrode and both endsin a gate width direction on an active region of a gate electrode of asecond transistor where the gate electrode is arranged at a fixedinterval from the forth additional gate pattern.

With this constitution, it is also possible to control fluctuation inshapes of gate electrodes of transistors by constituting gate electrodesof two transistors apart from each other with two additional gatepatterns and reduce a load by reducing a length of one of the additionalgate patterns.

The semiconductor device of the invention includes a semiconductordevice in which the first transistor has plural gate electrodes, thefirst gate electrode and the second gate electrode are arranged at bothends in a gate length direction in the active region of the firsttransistor, respectively, and the first additional gate pattern and thesecond additional gate pattern are arranged over both ends in a gatewidth direction of a first gate electrode and a second gate electrodearranged at a fixed distance from the first additional gate pattern andthe second additional gate pattern respectively.

With this constitution, it is possible to control fluctuation in shapesof gate electrodes and perform design with a less restriction on an areaby setting the first and the second additional gate pattern to a lengthin the gate width direction at least required for controllingfluctuation in shapes of the first and the second gate electrodes of thetransistors.

The semiconductor device of the invention includes a semiconductordevice in which the first additional gate pattern is arranged in aregion from both the ends in the gate width direction of the gateelectrode of the first transistor to both ends in a gate width directionon an active region of a gate electrode of a second transistor where agate electrode is arranged at a fixed interval from the first additionalgate pattern and which is arranged in parallel with the firsttransistor.

With this constitution, the first additional gate patterns are opposedto gate electrodes of adjacent two or more transistors. Thus, the firsttransistor and the second transistor share a first additional gatepattern as a dummy gate, whereby it is possible to reduce a man-hour forformation of additional gate patterns.

In the semiconductor device of the invention, the first additional gatepattern and the second additional gate pattern have different lengths byprojection parts from both the ends in the gate width direction of theactive region of the first transistor a fixed distance apart from thefirst additional gate pattern and the second additional gate pattern.

With this constitution, additional gate patterns are arranged withnecessary length according to a shape and an arrangement condition oftransistors and gate pattern, to selectively delete projection parts fora region that is limited by a rule between gate patterns including theadditional gate patterns in terms of an area. Thus, it is possible toshown an effect of dummy gates while preventing an increase in an areaand perform layout design that affects the other gate patterns less andwith which a layout area is reduced.

The semiconductor device of the invention includes a semiconductordevice in which a first transistor has plural gate electrodes, the firstand second additional gate patterns, which are formed at a fixeddistance from and in a process identical with that of gate electrodesarranged at both ends in a gate length direction of the firsttransistor, are arranged in an shape identical with that of the gateelectrodes, and a first gate electrode arranged on an active region ofthe first transistor is extended to an outside of an active region ofthe first transistor in a gate width direction of the first gateelectrode to range over at least both ends in a gate width direction onan active region of a second gate electrode arranged a fixed distanceapart from the first gate electrode.

With this structure, by arranging additional gate patterns for arequired region according to arrangement positions of gate electrodes ontransistors, since other gate patterns are less affected than arrangingadditional gate patterns with a certain length uniformly, it is possibleto perform layout design with a reduced area. In addition, by extendingthe first gate electrode without a man-hour for forming additional gatepatterns, the additional gate patterns can play a role of additionalgate patterns for the second gate electrode.

The semiconductor device of the invention includes a semiconductordevice in which a contact for connecting with a metal wiring layer isarranged in a position to which the first gate electrode is extended tothe outside of the active region.

With this constitution, it is possible to connect a contact region to aprojected part of any one of the gate electrodes as well according to apositional relation of a wiring of a metal layer and a gate pattern byextending gate electrodes without forming excess additional gatepatterns. Thus, since it is possible to perform layout designcorresponding to a layout restriction, as a result, it is possible toreduce a layout area.

The semiconductor device of the invention includes a semiconductordevice that includes a second transistor in addition to the firsttransistor and in which an additional gate pattern, which is arranged inparallel with and at a fixed distance from a gate electrode on an activeregion of the first transistor and a gate electrode of an active regionof the second transistor, formed in a process identical with that forthe gate electrodes of the first and the second transistors, and has acomposition identical with that of the gate electrodes, has differentlengths in a gate length direction of the first gate electrode stepwisein a region from both ends in a gate width direction on the activeregion of the gate electrode of the first transistor to both ends in agate width direction on the active region of the gate electrode of thesecond transistor.

With this structure, it is possible to realize a reduction in an overallarea by controlling an occupied area of the first additional gatepattern to be necessary minimum and securing an area in which other gatepatterns can be arranged.

In addition, when two additional gate patterns do not meet a designrule, the two additional gate patterns are connected while keepingshapes thereof. This makes it possible to secure an effect as additionalgate patterns and secure an arrangement area for other gate patternscompared with the case in which the additional gate patterns are formedsimply in a rectangular shape. Thus, it is possible to reduce a layoutarea.

In the semiconductor device of the invention, since the additional gatepatterns opposed to the gate electrodes of the first and the secondtransistors are arranged, it is unnecessary to consume a man-hour forcomplying with a design rule between additional gate patterns and formadditional gate patterns having a shape corresponding to the gateelectrodes of the respective transistors. Thus, it is possible toperform layout design with a less design man-hour.

In addition, with this constitution, a restriction of a design rulebetween additional gate patterns and gate patterns is prevented simplyby changing a length parts of the additional gate patterns opposed toprojected parts of gate electrode parts as required. Thus, it ispossible to reduce a man-hour and reduce an occupied area to performlayout design. Further, since the additional gate patterns are formed inrange opposed to the gate electrodes, it is needless to mention thatthere is an effect of controlling fluctuation in shapes.

A layout design method for a semiconductor device of the inventionincludes: a transistor forming step of arranging a transistor having oneor plural gate electrodes; and an additional gate pattern forming stepof forming an additional gate pattern in parallel with and at a fixeddistance from gate electrodes arranged at both ends in a gate lengthdirection of an active region of the transistor and in a length over atleast a gate width direction of the gate electrodes.

According to this layout design method, it is possible to arrangeadditional gate patterns proportionate to the arranged transistorautomatically and as many as necessary. Thus, it is possible performlayout design with high design efficiency and with a reduced area.

The layout method for a semiconductor device of the invention ischaracterized by including a transistor forming step of arranging atransistor having one or plural gate electrodes; and an additional gateforming step of forming first and second gate patterns that are formedin parallel with and at a fixed distance from the gate electrodes of thetransistor and in a process identical with that for the gate electrodesand has a composition identical with that of the gate electrodes, and inthat the first and the second additional gate patterns are formed to beallowed to be asymmetrical to the gate electrodes.

The first and the second additional gate patterns is possible to beformed and obtained in different regions in a gate width direction ofthe transistor.

According to this layout design method, an additional gate pattern isformed in a necessary area according to arrangement condition of gateelectrodes of transistors. Thus, there is an effect in a reduction of anarea compared with a layout design method of arranging additional gatepatterns in an identical shape and in an identical region at fixeddistance apart from a transistor.

In the layout design method, the transistor forming step or theadditional gate pattern forming step includes a step of extending afirst gate electrode included in the transistor to the outside of anactive region, at least to a range over both ends in a gate widthdirection on an active region of an adjacent second gate electrodearranged on the identical active region of the transistor.

According to this layout design method, when a gate electrode does notoppose to overall gate width portion of an adjacent gate electrode, itis necessary to arrange an additional gate pattern. However, since thegate electrode is extended to cope with the necessity, the layout designmethod leads to a reduction in a layout design man-hour.

The additional gate pattern forming step of the layout design method ofthe invention includes a step of, when the transistor includes a firstgate electrode and second and third gate electrodes arranged at a fixeddistance from the first gate electrode and the second gate electrode andthe third gate electrode are arranged linearly at an interval equal toor larger than the fixed distance in the gate width direction, extendinga projected part to the outside of an active region of the second gateelectrode and the third gate electrode or forming an additional gatepattern between the second gate electrode and the third gate electrode.

According to this layout design method, even when range of plural gateelectrodes in gate width direction has not enough to oppose to the bothend of adjacent gate electrode in identical transistor, it is possibleto judge whether an additional gate pattern is formed automatically or aprojected part of the gate electrode is extended to the outside of theactive region and realize the same effect as the additional gatepattern. Thus, it is possible to reduce a layout design man-hour.

A layout design method of the invention includes: a transistor formingstep of arranging a transistor having one or plural gate electrodes; anadditional gate pattern forming step of arranging an additional gatepattern in parallel with and at a fixed distance from gate electrodesarranged at both ends in a gate length direction of an active region ofthe transistor; and a connecting step of connecting a gate pattern tothe gate electrodes of the transistor or arranging a contact region. Theconnecting step includes a step of, when the gate pattern connectingwith the gate electrodes and the contact region are arranged within afixed distance from the first additional gate pattern, connecting thefirst additional gate pattern and the gate electrode or changing alength of the first additional gate pattern in the gate width directionto both the ends of the gate electrodes in active region of thetransistor.

According to this layout design method, even when the gate pattern orthe contact region connecting with the gate electrodes does not meet adesign rule between the gate pattern or the contact region and theadditional gate pattern, it is unnecessary to consider the design ruleby automatically connecting with the gate electrodes according to anarrangement condition for the gate pattern and the contact or changinglength of additional gate in region opposed to the projected part ofgate electrode. Thus, it is possible perform layout design with an areareduced efficiently.

In the layout design method of the invention, the connecting stepincludes a step of, if a length in the gate width direction of the gateelectrode of the first additional gate pattern connected to the gateelectrode of the transistor is equal to or longer than a fixed length,dividing the first additional gate pattern and arranging a fourthadditional pattern at a fixed distance from the first gate pattern.

According to this layout design method, since the additional gatepattern connecting with the gate electrode is equal to or longer than acertain length, the additional gate pattern is divided automatically andan additional gate pattern compensating for the additional gate patternis arranged. Thus, it is possible to control fluctuation of gateelectrodes and automatically perform layout design with less load of thegate electrode, at the time when the gate electrode is connected to theadditional gate pattern.

The layout design method of the invention further includes a moving stepof moving the transistor formed in the transistor forming step and theadditional gate pattern formed in the additional gate pattern formingstep while keeping an arrangement relation of the transistor and theadditional gate pattern.

According to this layout design method, even when the transistor has tobe moved because of an arrangement condition of a metal layer and gatepatterns around the transistor, it is possible to reduce a layout changeman-hour due to the movement of the transistor by moving the transistorand the additional gate pattern while keeping a positional relation ofthe transistor and the additional gate pattern.

The layout design method of the invention further includes an additionalgate pattern correcting step of, when the first and the secondadditional gate patterns formed in the additional gate pattern formingstep are arranged within a fixed distance, connecting the first and thesecond additional gate pattern.

According to this layout design method, when additional gate patterns donot meet a design rule, it is possible to perform layout design meetingthe design rule between the additional gate pattern by connecting theadditional gate patterns without consuming a design man-hour formovement and correcting transistors and gate patterns around theadditional gate patterns.

In the additional gate pattern correcting step of the layout designmethod of the invention, a shape of the first additional gate pattern orthe second additional gate pattern is changed or a fifth additional gatepattern is formed between the first and the second additional gatepatterns.

According to this layout design method, when additional gate patterns donot meet a design rule, if a part of the additional gate patterns cannotbe corrected or shapes of the additional gate patterns cannot becorrected because of a hierarchical structure of design data, it ispossible to correct the additional gate patterns while minimizing achange of the design data by forming an additional gate pattern anew.

In the additional gate pattern correcting step of the layout designmethod of the invention, the shape is changed or the additional gatepattern is formed such that only a region within a fixed distancebetween the first additional gate pattern and the second additional gatepattern are filled by the additional gate pattern.

According to this layout design, it is possible to correct design tomeet a design rule between additional gate patterns while the additionalgate pattern correcting step does not affect other gate patterns byperforming correction for minimizing the additional gate patterns interms of an area in order to meet the design rule between the additionalgate patterns.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram for explaining a layout design method for asemiconductor device in which additional gate patterns are arranged in afirst embodiment.

FIG. 2 is a layout diagram of a semiconductor device in which additionalgate patterns are arranged, designed by the layout design method in thefirst embodiment.

FIG. 3 is a layout diagram for the semiconductor device in which theadditional gate patterns are arranged, designed by the layout designmethod in the first embodiment.

FIG. 4 is a layout diagram for the semiconductor device in which theadditional gate patterns are arranged, designed by the layout designmethod in the first embodiment.

FIG. 5 is a layout diagram for the semiconductor device in which theadditional gate patterns are arranged, designed by the layout designmethod in the first embodiment.

FIG. 6 is a flow diagram for explaining a gate pattern connecting stepS300 in the first embodiment.

FIG. 7 is a layout diagram of a semiconductor device in which additionalgate patterns are arranged for explaining the gate pattern connectingstep S300 in the first embodiment.

FIG. 8 is a layout diagram of the semiconductor device in which theadditional gate patterns are arranged for explaining the gate patternconnecting step S300 in the first embodiment.

FIG. 9 is a layout diagram of the semiconductor device in which theadditional gate patterns are arranged for explaining the gate patternconnecting step S300 in the first embodiment.

FIG. 10 is a layout diagram of the semiconductor device in which theadditional gate patterns are arranged for explaining the gate patternconnecting step S300 in the first embodiment.

FIG. 11 is a layout diagram of the semiconductor device in which theadditional gate patterns are arranged for explaining the gate patternconnecting step S300 in the first embodiment.

FIG. 12 is a flow diagram for explaining a layout design method for asemiconductor device in which additional gate pattern are arranged in asecond embodiment.

FIG. 13 is a decode circuit of a general semiconductor device.

FIG. 14 is a layout of a semiconductor device, in which additional gatepatterns are arranged, designed by the layout design method in thesecond embodiment.

FIG. 15 is a layout of the semiconductor device, in which the additionalgate patterns are arranged, designed by the layout design method in thesecond embodiment.

FIG. 16 is a layout of the semiconductor device in which the additionalgate patterns are arranged, designed by the layout design method in thesecond embodiment.

FIG. 17 is a layout of the semiconductor device in which the additionalgate patterns are arranged, designed by the layout design method in thesecond embodiment.

FIG. 18 is a layout of the semiconductor device in which the additionalgate patterns are arranged, designed by the layout design method in thesecond embodiment.

FIG. 19 is a flow diagram for explaining a gate pattern connecting stepS300′ in the second embodiment.

FIG. 20 is a layout diagram of a semiconductor device in whichadditional gate patterns are arranged for explaining the gate patternconnecting step S300′ in the second embodiment.

FIG. 21 is a layout diagram of the semiconductor device in which theadditional gate patterns are arranged for explaining the gate patternconnecting step S300′ in the second embodiment.

FIG. 22 is a layout diagram of the semiconductor device in which theadditional gate patterns are arranged for explaining the gate patternconnecting step S300′ in the second embodiment.

FIG. 23 is a layout diagram of the semiconductor device in which theadditional gate patterns are arranged for explaining the gate patternconnecting step S300′ in the second embodiment.

FIG. 24 is a layout diagram of the semiconductor device in which theadditional gate patterns are arranged for explaining the gate patternconnecting step S300′ in the second embodiment.

FIG. 25 is a layout diagram of the semiconductor device in which theadditional gate patterns are arranged for explaining the gate patterncorrecting step S500′ in the second embodiment.

FIG. 26 is a layout diagram of the semiconductor device in which theadditional gate patterns are arranged for explaining the gate patterncorrecting s500′ in the second embodiment.

FIG. 27 is a flow diagram for explaining a layout design method for asemiconductor device in which additional gate patterns are arranged in athird embodiment.

FIG. 28 is a layout of a semiconductor device in which additional gatepatterns are arranged, designed by the layout design method in the thirdembodiment.

FIG. 29 is a layout of the semiconductor device in which the additionalgate patterns are arranged, designed by the layout design method in thethird embodiment.

FIG. 30 is a flow diagram for explaining an additional gate patternforming step S200′ in the third embodiment.

FIG. 31 is a flow diagram for explaining an internal additional gatepattern forming step S202 in the third embodiment.

FIG. 32 is a layout of a semiconductor device designed by a layoutdesign method in a fourth embodiment.

FIG. 33 is a latch circuit of a general semiconductor device.

FIG. 34 is a layout of a semiconductor device in which additional gatepatterns are arranged, created by a conventional layout design method.

FIG. 35 is a layout of the semiconductor device in which the additionalgate patterns are arranged, created by the conventional layout designmethod.

FIG. 36 is a layout of the semiconductor device in which the additionalgate patterns are arranged, created by the conventional layout designmethod.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A semiconductor device and a layout design method according toembodiments of the invention will be herein after explained in detailwith reference to the drawings.

First Embodiment

FIG. 1 is a diagram showing a flow of the layout design method of theinvention. After a transistor forming step S100, an additional gatepattern forming step S200 of forming an additional gate pattern servingas a dummy gate in parallel with and at a fixed distance from a gateelectrode of a transistor is performed, and a gate pattern connectingstep S300 of connecting a gate pattern or a gate contact region to theformed gate electrode of the transistor and arranging the gate patternor the gate contact region and a wiring step S400 of wiring a metallayer are executed. The respective steps will be herein after explainedwith layout design of a region surrounded by 33(A) of a latch circuitshown in FIG. 33 as an example.

FIG. 2 is a layout diagram of transistors TR1 to TR4 formed in thetransistor forming step S100. The transistors TR1 and TR3 have gateelectrodes GA1_1 to GA1_4 and GA3_1 to GA3_4 with different gate width.The transistors TR2 and TR4 have gate electrodes GA2_1 and GA2_2 as wellas GA4_1 and GA4_2 with the same gate width.

FIG. 3 is a layout diagram of additional gate patterns DG1 to 6 formedby the additional gate pattern forming step S200. The gate patterns DG1to 6 are arranged in a position a fixed distance SP_GA_L apart in a gatelength direction from the gate electrodes GA1_1, GA1_4, GA2_1, and GA2_2as well as GA3_1, GA3_4, GA4_1, and GA4_2 at both ends in a gate lengthdirection of the transistors TR1 and TR2 as well as TR3 and TR4, thatis, an x direction and are formed to occupy a region in the same gatewidth direction (a y direction in the figure) as indicated by analternate long and short dash line including a length of a projectionfrom an active region. Note that, in this example, a first additionalgate pattern, which is formed to be opposed to the gate electrode GA1_4,includes an additional gate patter, which is formed to be opposed toGA2_1, and is represented as DG2. Concerning DG5, similarly, anadditional gate pattern opposed to GA3_4 includes an additional gatepattern formed to be opposed to GA4_1. FIG. 3 is different from FIG. 34in that, instead of not forming dummy gate patterns on extended lines ina gate width direction of the gate electrodes GA1_2 and GA1_3 as well asGA3_2 and GA3_3, the gate electrodes GA1_2 and GA1_3 as well as GA3_2and GA3_3 are extended in a gate width direction (a −y direction in thefigure) to change a size in the gate width direction to include theadjacent gate electrodes GA1_1 and GA1_4 as well as GA3_1 and GA3_4 andprojected parts to the outside of active regions thereof.

FIG. 4 is a diagram in which the gate electrodes GA1_1 to GA1_4, GA2_1to GA2_2, GA3_1 to GA3_4, and GA4_1 to GA4_2 and the first additionalgate patterns or gate contact regions are connected. Gate contactregions CGMA1 to 4, 6 are connected to additional gate patterns DG1 to4, 6, respectively. Consequently, a design rule between gate patterns orgate contact regions connecting with additional gate patterns and gateelectrodes is eliminated. Thus, compared with FIG. 35, a restriction interms of an area of a layout by a design rule between gate patterns isreduced. The contact CGMA 2 is connected in a position extended to theoutside of active regions of the gate electrodes GA1_2 and GA1_3.

FIG. 6 is a diagram showing processing in the gate pattern connectingstep S300. The connecting step S300 includes a connection to gateelectrode step S301 of arranging and connecting a gate pattern or a gatecontact to a gate electrode of a transistor, a recognizing step S302 ofrecognizing an interval LGD between the arranged gate pattern or contactregion and the additional gate pattern and performing conditional branchof execution processing, and an additional gate pattern/gate patternconnecting step S303 of connecting the additional gate pattern and thegate electrode when the interval LGD is shorter than a fixed distanceSP_GA_min.

Processing in the gate pattern connecting step S300 will be explainedwith reference to FIGS. 7 to 11. FIG. 7 is an excerpt of only thesection of the transistor TR2 from FIG. 3.

First, the gate contact region CGMA3 is arranged to connect with thegate electrode GA2_2 (FIG. 8). In the case of this example, the gatecontact region CGMA3 is arranged near the additional gate pattern DG3 inorder to secure a fixed distance (SP_GA_min) or more from a gate patternGAP_21 connecting with the gate electrode GA2_1 and not to increase anarea. At this instance, in the recognizing step S302, it is recognizedthat LDG3<SP_GA_min from the interval LDG3 between the gate contactregion CGMA3 and the additional gate pattern DG3, and the step S303 ofconnecting the gate electrode GA2_2, the gate contact region CGMA3, andthe additional gate pattern DG3 from the conditional branch in therecognizing step in S302 is executed (FIG. 9).

Subsequently, the gate contact CGMA2 is connected to the gate electrodeGA2_1 via the gate pattern GAP2_1 in a position sufficiently distantfrom the additional gate pattern DG2 (FIG. 10). At this time, since thecontact CGMA2 and the gate pattern GAP2_1 are apart from the additionalgate pattern by SP_GA_min or more, respectively, the contact CGMA2 andthe gate pattern GAP2_1 are not connected. Here, in order to reduce anarea, the contact CGMA2 is moved in a + direction of a y axis in thefigure to be brought close to the additional gate pattern DG2. When thecontact CGMA2 is moved to a position where the distance LDG2 between theadditional gate pattern DG2 and the contact CGMA2 is LDG2<SP_GA_min,processing is performed in the recognizing step S302, and the additionalgate pattern, the gate pattern GAP_21, and the contact CGMA2 areconnected (FIG. 11). In this way, in the gate pattern connecting stepS300, when a gate pattern or a contact region are connected to a gateelectrode or when a gate pattern or a contact region connecting with agate electrode are moved, if a distance between the gate pattern or thecontact region and the additional gate pattern is reduced to the fixeddistance SP_GA_min or less, processing connection with the additionalgate pattern is automatically executed. Thus, a designer is capable ofperforming layout design without being conscious of a design rulebetween the gate pattern or the contact region and the additional gatepattern. Moreover, the additional pattern/gate electrode connecting stepS303 of connecting the additional gate pattern and the gate electrodeincludes a step of converting an additional gate pattern, which isusually arranged as a dummy gate defined differently from the gateelectrode as layout data because of mask processing or the like, into anidentical definition as the gate electrode once. Thus, the designer iscapable of connecting the additional gate pattern and the gate electrodewithout consuming a man-hour required for the conversion.

As opposed to FIG. 4, FIG. 5 is a diagram in which wiring is made withone layer of metal in the wiring step S400. Note that it is assumed thatwiring with a power supply is made with not-shown two layers of metal.

Here, the CGMA3 is arranged in a position different from that in FIG. 9because an area is smaller from a spacing rule of one-layer metal or thelike when the CGMA3 is arranged such that a contact is arranged in thegate width direction of the gate electrode, in this case, in the ydirection in the figure on the additional gate pattern.

When FIG. 5 and FIG. 36 are compared, it is seen that lengths in the xand y directions in the figure are reduced because the gate contactregion is arranged on the additional gate pattern and the spacing rulebetween the additional gate pattern and the gate electrode iseliminated. In addition, in FIG. 36, only one contact can be arranged inthe gate contact regions CGMA 22 and 24 to 28 because of the restrictionof the design rule. On the other hand, in FIG. 5, since the gate patternwith the gate electrode extended to the outside of the active region andthe gate contact region CGMA2 are connected and the gate electrode andthe additional gate pattern are connected, it is possible to arrange twocontacts without increasing an area. In addition, since it is possibleto connect a signal line with one layer of metal, signal wiring intwo-layer metal is not affected. Thus, it is possible to prevent anincrease in an area due to a wiring restriction in the two-layer metal.

In this way, according to the layout design method in the firstembodiment of the invention, the transistor is arranged, the additionalgate pattern with the same shape as the gate electrodes arranged at boththe ends in the gate length direction of the transistor is automaticallyformed or the gate electrodes are automatically extended to the outsideof the active region in a form of including adjacent gate electrodes inthe gate width direction, and the gate pattern or the gate contactregion connecting with the gate electrodes and the additional gatepattern is automatically connected according to an arrangement positionbetween the gate pattern or the gate contact region and the additionalgate pattern. Thus, it is possible to reduce a design man-hour of thesemiconductor device in which the additional gate pattern is arranged.Moreover, since the gate electrodes and the additional gate pattern areconnected, it is possible to perform layout design with an area reduced.

It is possible to implement the additional gate pattern forming step andthe gate pattern connecting step described in the invention bydeveloping a program for the function of performing conditional branchfrom arrangement information of the gate electrode of the transistor,the contact region connecting with the gate electrode, and the patternof the gate electrode and the additional gate pattern using a logicalarithmetic operation or a function of holding arrangement information ofthe additional gate pattern and the gate contact region as a part ofshapes of formed transistors and conditionally branching presence orabsence of connection from a positional relation between the shapes.

Note that in this embodiment, in the additional gate pattern formingstep S200, when gate widths of adjacent gate electrodes on an identicaltransistor are different, projected parts of the adjacent gateelectrodes are extended to the outside of active regions so as to rangeregions on the active regions of the gate electrodes in the gate widthdirection. However, it is needless to mention that the same processingis also executed when the position of both ends in the gate widthdirection of the active regions of the adjacent gate electrodes aredifferent even if gate widths are the same.

In this embodiment, in the additional gate pattern forming step S200,when gate widths of adjacent gate electrodes on an identical transistorare different, projected parts of the adjacent gate electrode areextended to the outside of active regions so as to range regions on theactive regions of the gate electrodes. However, an additional gatepattern may be formed so as to range regions on the active regions ofthe adjacent gate electrodes. In this case, although a degree of freedomof layout design is deteriorated, there is an effect that a load isreduced because the gate electrodes are not extended.

Second Embodiment

FIG. 12 is a diagram showing a flow of a layout design method accordingto a second embodiment of the invention. The layout design method in thesecond embodiment is different from the layout design method describedin the first embodiment in that a transistor moving step S250 of movinga transistor is added after the additional gate pattern forming stepS200, an additional gate pattern correcting step S500 of correcting ashape or adding an additional gate pattern anew such that the additionalgate pattern arranged as the dummy gate meets the design rule is addedafter the wiring step S400, and a gate pattern connecting step S300′ isa partially corrected version of the gate pattern connecting step S300in the first embodiment. The layout design method in this embodimentwill be herein after explained centering on the steps changed from thefirst embodiment with layout design of a buffer section 13(A) of adecoder circuit shown in FIG. 13 as an example.

FIG. 14 is a layout diagram in which transistors TR5 to TR7 are formedin the transistor forming step S100 and, then, additional gate patternsDG11 to 16 serving as dummy gate are formed in the additional gatepattern forming step S200. As indicated by an alternate long and shortdash line, the additional gate patterns DG11 to 16 are formed in a sizeincluding regions on active regions of gate electrodes on both ends in agate length direction of the transistor TR5 to 7 and lengths ofprojections. P_N1 and P_N2 are input pins. It is considered desirable tomove TR5 and TR6 in a direction shown in the figure because ofarrangement positions of the input pins and a spacing rule of metal.

FIG. 15 is a diagram in which the transistors TR5 and TR6 are moved inthe transistor moving step S250. The transistor moving step S250 is astep of moving transistors and additional gate patterns arranged at afixed distance from gate electrodes of the transistors while maintaininga positional relation. Even if the transistors TR5 and TR6 are moved in−x and +x directions in the figure, respectively, the positionalrelation between the transistors TR5 and TR6 and the additional gatepatterns DG11 and 12 as well as DG13 and DG14 are maintained.

When one additional gate pattern arranged as dummy gate are arranged ina form of including range of gate electrodes of two transistors, whichare arranged a fixed distance apart from the additional gate pattern, ina gate width direction, in the transistor moving step S250, thetransistors are moved while keeping a positional relation between theadditional gate pattern of a size proportionate to the gate electrode ofthe respective transistors and the transistors.

FIG. 16 is a diagram in which gate electrodes, additional gate patterns,and gate contact regions are connected in the gate pattern connectingstep S300′. Since input pins are arranged in a lower left and a lowerright of a screen, gate electrodes GA5_1 and GA7_1 as well as GA6_2 andGA7_8 are connected by gate patterns GA_51 and GA_62 and gate contactregions CGMA11 and CGMA14 and arranged in a place near additional gatepatterns DG11 and DG14. The second embodiment is different from thefirst embodiment in that the additional gate patterns DG11 and DG14recognizes a distance from gate contact regions and automaticallydeletes sections opposed to projected parts from active regions of gateelectrodes of transistors.

FIG. 19 is a diagram showing processing in the gate pattern connectingstep 300′. The gate pattern connecting step S300′ is different from thegate pattern connecting step S300 in the first embodiment in that, asize changing step S304 of deleting the projected parts of theadditional gate patterns arranged as the dummy gate when the relationbetween the interval LGD between gate patterns and the length EXT_GD ofthe projected part from the active regions of the gate electrodes andthe minimum spacing rule SP_GA_min between the gate patterns meet thecondition of SP_GA_min-EXT_GD<LGD<SP_GA_min in the recognizing stepS302, a judging step S305 of judging whether the additional gatepatterns can be divided from a shape of the additional gate patternsserving as the dummy gates connected to the gate electrodes after theadditional gate/gate pattern connecting step S303 executed whenLGD<SP_GA_min-EXT_WD after the recognizing step S302, and an additionalgate pattern dividing step S306 of dividing the additional gate patternsinto two when the condition in S305 is met are added.

In FIGS. 20 to 26, the processing in the gate pattern connecting stepS300′ is explained centering on added parts. In FIG. 20, the transistorsTR6 and TR7 and apart of the additional gate patterns are excerpted fromFIG. 15.

First, the gate electrodes GA6_2 and GA7_6 are connected by a gatepattern GAP_62. Since an input pin is in a lower left in the figure andan output node is on a right side in a screen, a gate contact regionCGMA14 is arranged on GAP 62 and is moved around additional gate patternDG14 serving as a dummy gate is moved to around DG14 (FIG. 21).

When a distance LdG_14 between the additional gate pattern DG14 and thegate contact region CGMA14 is in a relation ofSP_GA_min-EXT_GD<LDG14<SP_GA_min, the dummy gate size changing step S304is executed from the conditional branch in the recognizing step in S302to change a length of the additional gate pattern DG14 until an upperend in a y direction of an active region of the gate electrode GA6_2,that is, deleting the part of gate pattern DG14 opposed to a projectedpart from the active region of gate electrode GA6_2 (FIG. 22).

As opposed to FIG. 16, FIG. 17 is a diagram in which wiring is made byone-layer metal in the wiring step S400. Note that it is assumed thatpower supply wiring is made by not-shown two-layer metal. After thiswiring ends, if a design rule is not met between additional gatepatterns arranged as dummy gates and both the additional gate patternsare in floating or a power supply or ground potential, the additionalgate pattern correcting step S500 of correcting and adding an additionalgate pattern is executed. In FIG. 17, since additional gate patternsDG12 and DG13 do not meet the spacing rule SP_GA_min, in the additionalgate pattern correcting step S500, formation of a new additional gatepattern filling a space between DG12 and DG13 or size change of theadditional gate patterns DG12 and DG13 is executed.

FIG. 18 is a diagram in which the additional gate pattern correctingstep S500 is executed from FIG. 17. An additional gate pattern DG17 isformed anew to avoid a violation of a spacing rule between theadditional gate patterns DG12 and DG13.

In order to give a supplementary explanation about the gate patternconnecting step, a case in which the gate contact region CGMA14 isbrought closer to the additional gate pattern DG14 will be explained.When the distance LDG14 between the gate contact region CGMA14 and theadditional gate pattern DG4 meet the condition LDG14<SP_GA_min-EXT_WD,the additional gate/gate pattern connecting step S303 is executed fromthe result of the conditional branch in the recognizing step S302 andthe gate contact region CGMA14 and the additional gate pattern DG14 areconnected (FIG. 23). Next, in the judging step S305, it is judgedwhether it is possible to divide the connected additional gate pattern.As a judgment condition, for example, a length in y direction of anadditional gate pattern arranged at a width in x direction LG_min froman end is longer than a sum of a minimum line length WG_min calculatedfrom a minimum area and a minimum width of a gate pattern and a gatepattern minimum interval SP_GA_min. When this condition is met, theadditional gate pattern dividing step S306 is executed, and theadditional gate pattern DG14 is divided into an additional gate patternDG18 connecting with a gate electrode and an additional gate patternDG19 that does not connect with the gate electrode and is floating interms of a potential while complying with the spacing rule SP_GA_min(FIG. 24).

In this way, according to the layout design method in the secondembodiment of the invention, a length of an additional gate pattern ischanged or connected to a gate electrode or divided according to anarrangement condition between an additional gate pattern connecting witha gate electrode, a gate contact region, and an additional gate patternarranged as a dummy gate. When the additional gate patters do not meet adesign rule, a shape of the additional gate patterns is corrected or anadditional gate pattern is arranged anew to meet the design ruleautomatically, whereby a designer can perform layout design withoutbeing conscious of a design rule concerning the additional gate patternarranged as the dummy gate. Thus, it is possible to reduce a layoutdesign man-hour for a semiconductor device. Moreover, since theadditional gate pattern connecting with the gate electrode is dividedautomatically, in particular, when the gate electrode is connected to anadditional gate pattern adjacent to a transistor with a large gatewidth, it is possible to perform layout design with a reduced load in aless man-hour.

Note that in order to perform layout design with a reduced load throughconnection with an additional gate pattern, it is desirable to select anadditional gate pattern with a smaller area among additional gatepatterns arranged at a fixed distance from a gate electrode of atransistor.

In this embodiment, the additional gate pattern DG17 with a size in thegate width direction equal to that of the additional gate patterns DG12and DG13 is formed in the additional gate pattern correcting step.However, when lengths of additional gate patterns violating a designrule are different or when arrangement position in the gate widthdirection (the y direction in the figure) are different, only sectionsviolating the design rule are corrected.

In FIG. 25, only the transistors TR5 and 6 are excerpted from FIG. 14.FIG. 25 is different from FIG. 14 in that an arrangement relation of TR5and Tr6 is deviated by ΔY in the y direction in the figure.

As opposed to FIG. 25, in FIG. 26, the additional gate patterncorrecting step S500 is executed. In this additional gate patterncorrecting step, an additional gate pattern DG20 is formed anew for arange of (A11), in which design rule error actually occurs, in order toavoid the design rule. By carrying out a minimum change in order toavoid the design rule in this way, it is possible to avoid violation ofthe design rule in the correcting step without affecting otheradditional gate patterns used for connection with the gate electrode orthe like.

Note that, in this embodiment, in the additional gate pattern correctingstep S500, violation of the design rule is avoided by forming anadditional gate pattern anew. However, an avoidance method for changinga shape of an additional gate pattern to meet a design rule may be used.Moreover, in this embodiment, the additional gate pattern correctingstep is performed after creating a unit cell. However, the additionalgate pattern correcting step S500 may be performed in a higher orderdesign hierarchy, in which plural unit cells are arranged, in order tomeet a design rule between additional gate patterns arranged in the unitcells.

In FIG. 24, a transistor is not shown in the −x direction of TR6.However, it is needless to mention that, when a transistor TR6′ ispresent in the −x direction of TR6 and an additional gate patternserving as a dummy gate of TR6′ is present on a line identical with thatof DG14 or when the additional gate pattern and DG14 do not meet aseparation rule between gate patterns and are formed as identicaladditional gate patterns, the additional gate pattern DG19 cut for areduction of a load and the additional gate pattern DG18 connecting withthe gate electrode GA6_2 are formed to be arranged over both ends in thegate width direction of gate electrodes of both TR6 and TR6′, wherebythe two gate patterns has an effect of controlling fluctuation in shapesfor the gate electrodes of the two transistors.

Third Embodiment

FIG. 27 is a diagram showing a flow of a layout design method accordingto a third embodiment of the invention. The layout design method in thethird embodiment is different from the layout design method described inthe second embodiment in that an additional gate pattern forming stepS200′ is a partially corrected version of the additional gate patternforming step S200′ in the second embodiment. The layout design method inthis embodiment will be herein after explained concerning only changedsteps.

FIG. 28 is a layout diagram in which a transistor TR8 is formed in thetransistor forming step S100. Gate electrodes GA8_1 to 3 are arranged onthe transistor TR8 and the gate electrodes GA8_2 and GA8_3 are arrangedlinearly and share a source region S8_1.

FIG. 30 is a diagram showing a flow of the additional gate patternforming step S200′. The additional gate pattern forming step S200′consists of an external additional gate pattern forming step S201 ofarranging an additional gate pattern serving as a dummy gate at a fixeddistance from gate electrodes at both ends in a gate length direction ofa transistor and an internal additional gate pattern forming step S202of, when gate electrodes adjacent to an object gate electrode are notarranged in an area over both ends in a gate width direction of theobject gate electrode for all the gate electrodes of the transistor,extending the gate electrodes or forming an additional gate pattern.FIG. 31 is a diagram showing a flow of the internal additional gatepattern forming step S202. The internal additional gate pattern formingstep S202 consists of a judging step S202_1 of judging whether anadjacent gate electrode on one side and a projected part thereof arearranged in an entire area over both ends in the gate width direction ofthe gate electrodes for all the gate electrodes, a gate electrodeextending step S202_2 of, when adjacent gate electrode and the projectedpart thereof are not arranged in a entire region on both ends in gatewidth direction of the gate electrode, if the gate electrode on one sideis one gate electrode, extending an adjacent gate electrode as it is, asecond judging step S202_3 of performing conditional branch concerningwhether there are two adjacent gate electrodes on one side and aninterval in the gate width direction is larger than a sum of a space twotimes as large as that in a minimum spacing rule between gate patternsand a minimum gate line length WG_min determined from a minimum area, aforming step S202_4 of forming an additional gate pattern as a dummygate between the two gate electrode when the condition is met, and astep S202_5 of extending adjacent gate electrodes to the outside ofactive regions when the condition is not met.

FIGS. 28 and 29 are diagrams showing a layout in which additional gatepatterns are arranged in the additional gate pattern forming step S200′.First, the external additional gate pattern forming step S201 isexecuted and additional gate patterns DG18 to 20 are formed at a fixeddistance from gate electrodes GA8_1 to 3 on a transistor TR8 so as toinclude areas on active regions of the gate electrodes GA8_1 to 3 andprojected parts in a gate width direction (FIG. 28). Next, since theregion of the gate electrodes GA8_2 and GA8_3, and the projected partsthereof in the gate width direction are not arranged in an entire regionover both ends in the gate width direction of the gate electrode GA8_1and an interval between the gate electrodes GA8_2 and GA8_3 meet thecondition, in the internal additional gate pattern forming step, a gatepattern DG21 is arranged in a form of meeting the minimum spacing ruleSP_GA_min on an extended line of GA8_2 and GA8_3 (FIG. 29). If theinterval between GA8_2 and GA8_3 does not meet the condition, processingfor extending the gate electrode GA8_2 and GA8_3 is executed.

In this way, according to the layout design method in the thirdembodiment of the invention, even when source and drain transistor areadjacent to two or more gate electrodes according to arrangementpositions and a shape of gate electrodes of arranged transistors, it ispossible to reduce a layout design man-hour by automatically performingformation of an additional gate pattern serving as a dummy gate betweenthe gate electrodes or extension of the gate electrodes to the outsideof the active regions.

Fourth Embodiment

FIG. 32 is a diagram showing a layout according to a fourth embodimentof the invention. TR9 is an N channel transistor formed on a PWELLhaving gate electrodes GA9_1 to 6. Here, GA9_1 and GA9_6 among the gateelectrodes are fixed to a power supply potential and active regionsindicated by shade and active regions adjacent to the gate electrodesGA9_1 and GA9_6 are connected to a ground potential. Thus, the regionssubstantially work as capacitive components of the power supplypotential and the ground potential. Since the gate electrodes GA9_1 toGA9_6 are arranged such that gate patterns are arranged uniformly withthe gate electrodes GA9_2 to 5, which operate dynamically, in a gatelength direction (an x direction in the figure) with the GA9_1 and GA9_6at both ends, it is possible to control fluctuation in the gateelectrodes GA9_2 to GA9_5 affecting an actual circuit operation to besmall. In addition, since an active region, which actually operates, isalso surrounded by the active regions indicated by shade, which work ascapacitors, it is possible to control decline in ability due tofluctuation and stress.

In this way, according to the layout design method in the fourthembodiment of the invention, additional gate patterns are provided onactive region and connected to a power supply potential and activeregions, which does not perform a dynamic operation, are provided atboth ends of the transistor. Thus, although an area increases, it ispossible to control fluctuation in shapes of gate electrodes of thetransistor and fluctuation in a current ability of the transistor. Inaddition, since gate patterns at both ends are present on active regionsin the gate length direction and fixed to the power supply potential andactive regions adjacent to the active regions are fixed to the groundpotential, there is an effect that the active regions work as capacitivecomponents for fixing a power supply.

Note that, in this embodiment, in the N channel transistor created inthe PWELL region, the gate electrodes are fixed to the power supplypotential and the active regions at both the ends are fixed to theground potential. However, it is needless to mention that potentialsconnected to formed regions, gate electrodes, and active regions may bedifferent.

The semiconductor device and the layout design method according to theinvention is advantageous for a reduction in a design man-hour and areduction in an area in a semiconductor device in which additional gatepatterns are arranged as dummy gate to control fluctuation in gateelectrodes.

1. A semiconductor device, comprising: a first transistor regionincluding a first active region and a plurality of first gate electrodesextending in a first direction, the plurality of first gate electrodesharing the first active region; a second transistor region including asecond active region and a plurality of second gate electrodes extendingin the first direction, the plurality of second gate electrode sharingthe second active region; dummy gate patterns extending in the firstdirection and sandwiching the first transistor region and the secondtransistor region, the dummy gate patterns being arranged in parallelwith the plurality of first gate electrodes and the plurality of secondgate electrodes; and a shared dummy gate pattern extending in the firstdirection and located between the first and second transistor regionsand being adjacent to the first transistor regions and to the secondtransistor regions, wherein: a width of the first active region in thefirst direction at a first gate electrode which is a closest gateelectrode to the shared dummy pattern among the plurality of first gateelectrodes is longer than a width of the second active region in thefirst direction at a second gate electrode which is a closest gateelectrode to the shared dummy pattern among the plurality of second gateelectrodes, a first gate width of the first gate electrode on the firstactive region in the first direction is longer than a second gate widthof the second gate electrode on the second active region in the firstdirection, a length of the shared dummy gate pattern in the firstdirection is equal to or longer than the first gate width, and is longerthan the second gate width, the dummy gate patterns includes a firstdummy gate pattern and a second dummy gate pattern, the first dummy gatepattern and the shared dummy gate pattern sandwiches the firsttransistor region, and the second dummy gate pattern and the shareddummy gate pattern sandwiches the second transistor region, and a lengthof the first dummy gate pattern in the first direction is longer than alength of the second dummy gate pattern in the first direction.
 2. Thesemiconductor device according to claim 1, wherein a gate length of theshared dummy gate pattern in a second direction perpendicular to thefirst direction is longer than a gate length of the first gate electrodeand a gate length of the second gate electrode in the second direction.3. The semiconductor device according to claim 1, wherein a gate lengthof the shared dummy gate pattern varies along a second directionperpendicular to the first direction.
 4. The semiconductor deviceaccording to claim 1, wherein: the width of the first active regionvaries along a second direction perpendicular to the first direction,and the gate width of the first transistor is longer than a longest partof the first active region in the first direction.
 5. The semiconductordevice according to claim 1, wherein there is only one shared dummy gatepattern between the first and second transistor regions.